#include <vector>
#include <algorithm>
#include <cmath>

// Define real type (float in this case)
using Real = float;

// Constants and configuration
constexpr int MAXMPROC = 1024;  // Maximum number of MPI processes
constexpr int MAXNPROC = 1024;  // Maximum number of SMP processes
constexpr int NUMNP = 1000000;  // Maximum number of nodes (adjust as needed)

class CTNSSearch {
public:
    // Main search routine
    void operator()(
        int localsFlag,          // Local slideline flag (0=global, 1=local)
        int& totalPotentialPairs, // Output: Total number of potential contact pairs
        const std::vector<Real>& nodeCoords, // Input: Nodal coordinates (3 x NUMNP)
        const std::vector<int>& segmentConnectivity, // Input: Master segment connectivity (6 x numSegments)
        int maxBuckets,          // Maximum number of buckets for spatial partitioning
        const std::vector<int>& globalNodeNumbers, // Global node numbering
        int numPenetratingNodes,  // Number of nodes that may penetrate
        std::vector<int>& segmentPointers, // Output: Segment pointers to contact pairs
        int contactAccelerator,   // Contact search accelerator flag
        const std::vector<int>& internalSlaveNodes, // Internal slave node list
        const std::vector<int>& pointerList, // Pointer for insect list (type 37)
        const std::vector<int>& projectionList, // Projection list (type 37)
        const std::vector<Real>& segmentThickness, // Segment thickness values
        const std::vector<Real>& nodeThickness,    // Node thickness values
        Real contactThickness,    // Contact thickness parameter
        int numGlobalSlaveNodes,  // Number of global slave nodes
        int numInternalSegments,   // Number of internal master segments
        const std::vector<int>& flagTable, // Zero-filled flag table
        std::vector<int>& processControl, // MPI process control data
        int slidelineType,        // Type of slideline contact
        int slidelineNumber,      // Slide line number (sequential)
        int& totalSlaveNodes,     // Total number of slave nodes (internal + remote)
        int& maxPairsPerProcess,   // Maximum number of pairs per SMP process
        Real thicknessExtension,   // Thickness extension for search
        Real frictionCoefficient,  // Friction coefficient
        Real separationThreshold  // Separation threshold for search (1.5 for FORM, 1.0 for CRASH)
    ) {
        // Local variables
        std::vector<int> nodesSentPerProcess(MAXMPROC); // Number of nodes sent per MPI process
        std::vector<int> nodesReceivedPerProcess(MAXMPROC); // Number of nodes received per MPI process
        Real globalBucketBounds[3][3]; // Global bucket limits for spatial partitioning
        int numBuckets[3]; // Number of buckets in X,Y,Z directions
        std::vector<std::array<int, 2>> communicationFlags(MAXMPROC); // Flags to skip sends/receives
        std::vector<int> pairsPerProcess(MAXNPROC); // Number of pairs per SMP process
        
        // Calculate search threshold based on thickness parameters
        Real searchThreshold = separationThreshold * (contactThickness + thicknessExtension);
        
        // Step 1: Perform bucket sort for spatial partitioning
        bucketSort(
            localsFlag, slidelineNumber, searchThreshold,
            internalSlaveNodes.size(), numGlobalSlaveNodes, totalSlaveNodes,
            numInternalSegments, maxBuckets, nodeCoords,
            segmentConnectivity, internalSlaveNodes, globalNodeNumbers,
            segmentThickness, nodeThickness, processControl,
            nodesSentPerProcess, nodesReceivedPerProcess, communicationFlags,
            globalBucketBounds, numBuckets
        );
        
        // Step 2: Build potential contact pair lists
        int workArraySize = 4 * totalSlaveNodes * numProcesses_;
        if (workArraySize > maxWorkArraySize_) {
            resizeWorkArrays(workArraySize);
            maxWorkArraySize_ = workArraySize;
        }
        
        // Calculate block size for parallel processing
        int blockSize = (numInternalSegments + numProcesses_ - 1) / numProcesses_;
        
        // Parallel processing of segments to find potential contacts
        #pragma omp parallel for
        for (int proc = 0; proc < numProcesses_; proc++) {
            int segmentStart = proc * blockSize;
            int segmentEnd = std::min(numInternalSegments, (proc + 1) * blockSize);
            
            int nodeOffset = 4 * totalSlaveNodes * proc;
            int imNodeOffset = nodeOffset;
            int jmNodeOffset = nodeOffset + totalSlaveNodes;
            int ipassOffset = nodeOffset + 2 * totalSlaveNodes;
            int ipass2Offset = nodeOffset + 3 * totalSlaveNodes;
            
            buildPotentialPairList(
                localsFlag, proc, segmentStart, segmentEnd, 
                pairsPerProcess[proc], slidelineType, searchThreshold,
                contactThickness, thicknessExtension, numGlobalSlaveNodes,
                numInternalSegments, nodeCoords, segmentConnectivity,
                flagTable, segmentThickness, segmentPointers, pointerList,
                projectionList, globalBucketBounds, numBuckets, totalSlaveNodes,
                globalNodeNumbers, /* spatialBox */, /* bounds */, 
                /* bucketTable */, /* segmentData */, /* directions */,
                /* areas */, /* bucketList */, /* nodeData */,
                /* contactPairs */, /* orientations */, /* localCoords */,
                /* segmentList */, maxPairsPerProcess_,
                workArray1_.data() + imNodeOffset,
                workArray1_.data() + jmNodeOffset,
                workArray1_.data() + ipassOffset,
                workArray1_.data() + ipass2Offset
            );
        }
        
        // Step 3: Process results and check for buffer overflows
        processResults(
            localsFlag, pairsPerProcess, totalPotentialPairs, maxPairsPerProcess,
            numInternalSegments, frictionCoefficient, segmentPointers,
            nodesSentPerProcess, nodesReceivedPerProcess, communicationFlags,
            processControl, numGlobalSlaveNodes
        );
    }

private:
    // Member variables
    int numProcesses_;             // Number of SMP processes
    int maxWorkArraySize_;         // Current size of work arrays
    int maxPairsPerProcess_;       // Maximum pairs per process
    std::vector<int> workArray1_;  // Primary work array
    
    // Helper methods
    void bucketSort(
        int localsFlag, int slidelineNumber, Real searchThreshold,
        int numInternalSlaveNodes, int numGlobalSlaveNodes, int& totalSlaveNodes,
        int numInternalSegments, int maxBuckets, const std::vector<Real>& nodeCoords,
        const std::vector<int>& segmentConnectivity, const std::vector<int>& internalSlaveNodes,
        const std::vector<int>& globalNodeNumbers, const std::vector<Real>& segmentThickness,
        const std::vector<Real>& nodeThickness, std::vector<int>& processControl,
        std::vector<int>& nodesSentPerProcess, std::vector<int>& nodesReceivedPerProcess,
        std::vector<std::array<int, 2>>& communicationFlags, Real globalBucketBounds[3][3],
        int numBuckets[3]
    ) {
        // Implementation of spatial partitioning using bucket sort
        // This divides the domain into buckets for efficient contact search
        
        // 1. Calculate global bounds of the model
        calculateGlobalBounds(nodeCoords, globalBucketBounds);
        
        // 2. Determine optimal number of buckets in each direction
        determineBucketCounts(globalBucketBounds, maxBuckets, numBuckets, searchThreshold);
        
        // 3. Assign nodes and segments to buckets
        assignToBuckets(nodeCoords, segmentConnectivity, internalSlaveNodes, 
                       globalBucketBounds, numBuckets, searchThreshold);
        
        // 4. For distributed memory parallel (DMP) version:
        if (localsFlag == 0) {
            exchangeBoundaryData(nodesSentPerProcess, nodesReceivedPerProcess, 
                               communicationFlags, processControl);
        }
    }
    
    void buildPotentialPairList(
        int localsFlag, int processId, int segmentStart, int segmentEnd,
        int& pairsForProcess, int slidelineType, Real searchThreshold,
        Real contactThickness, Real thicknessExtension, int numGlobalSlaveNodes,
        int numInternalSegments, const std::vector<Real>& nodeCoords,
        const std::vector<int>& segmentConnectivity, const std::vector<int>& flagTable,
        const std::vector<Real>& segmentThickness, std::vector<int>& segmentPointers,
        const std::vector<int>& pointerList, const std::vector<int>& projectionList,
        Real globalBucketBounds[3][3], int numBuckets[3], int totalSlaveNodes,
        const std::vector<int>& globalNodeNumbers, /* various spatial data structures */,
        int maxPairsPerProcess, int* imNodes, int* jmNodes, 
        int* ipassData, int* ipass2Data
    ) {
        // Implementation of potential contact pair detection
        
        // 1. For each segment in the assigned range
        for (int seg = segmentStart; seg < segmentEnd; seg++) {
            // 2. Find nodes in nearby buckets that might contact this segment
            findNearbyNodes(seg, globalBucketBounds, numBuckets, searchThreshold);
            
            // 3. For each candidate node, perform detailed contact check
            for (auto node : candidateNodes) {
                if (checkContactCondition(node, seg, nodeCoords, segmentConnectivity,
                                        contactThickness, thicknessExtension)) {
                    // 4. Store valid contact pairs
                    storeContactPair(processId, pairsForProcess, node, seg);
                }
            }
        }
    }
    
    void processResults(
        int localsFlag, const std::vector<int>& pairsPerProcess,
        int& totalPotentialPairs, int& maxPairsPerProcess, int numInternalSegments,
        Real frictionCoefficient, std::vector<int>& segmentPointers,
        const std::vector<int>& nodesSentPerProcess, const std::vector<int>& nodesReceivedPerProcess,
        const std::vector<std::array<int, 2>>& communicationFlags,
        std::vector<int>& processControl, int numGlobalSlaveNodes
    ) {
        // 1. Calculate total and maximum pairs
        totalPotentialPairs = 0;
        maxPairsPerProcess = 0;
        for (int count : pairsPerProcess) {
            totalPotentialPairs += count;
            maxPairsPerProcess = std::max(maxPairsPerProcess, count);
        }
        
        // 2. Check for buffer overflows and resize if needed
        if (maxPairsPerProcess > maxPairsPerProcess_) {
            resizePairBuffers(maxPairsPerProcess);
            maxPairsPerProcess_ = maxPairsPerProcess;
            // Would typically return to reprocess in real code
        }
        
        // 3. Check total pairs against permanent array sizes
        if (totalPotentialPairs > maxTotalPairs_) {
            resizePermanentArrays(totalPotentialPairs, frictionCoefficient);
            maxTotalPairs_ = totalPotentialPairs;
        }
        
        // 4. Check against scratch array sizes
        if (totalPotentialPairs > maxScratchPairs_) {
            resizeScratchArrays(totalPotentialPairs);
            maxScratchPairs_ = totalPotentialPairs;
        }
        
        // 5. Store new search list information
        storeSearchResults(pairsPerProcess, numInternalSegments, segmentPointers);
        
        // 6. For DMP version: sort search list by process number
        if (localsFlag == 0) {
            sortByProcess(totalPotentialPairs, numGlobalSlaveNodes, nodesSentPerProcess,
                         nodesReceivedPerProcess, communicationFlags, processControl);
        }
        
        // 7. Restore original node numbering
        restoreNodeNumbers(totalPotentialPairs, localsFlag);
    }
    
    // Additional helper methods would be implemented here...
};